Some 2,200 guests filled the Washington National Cathedral on Tuesday morning for the inaugural prayer service, a tradition as old as the country itself.The service is meant to provide a spiritual boost to the newly sworn-in president. Prominent national clergy — from the Protestant, Catholic, Orthodox Christian, Muslim, Jewish and Sikh traditions — will offer prayers to Obama, who is accompanied by first lady Michelle Obama, Vice President Biden and Jill Biden.“The reason we come together to pray is because we want the best for our country,” said Cardinal Donald Wuerl, the archbishop of the Washington Catholic archdiocese, as he entered the cathedral early Tuesday. “We pray for our president, we pray for our vice president. We pray for our leaders as we move forward.”Among those participating in the service at the cathedral are: Wuerl; the Rev. Katharine Jefferts Schori, presiding bishop of the Episcopal Church; Imam Mohamed Magid, president of the Islamic Society of North America and leader of the Sterling mega-mosque All Dulles Area Muslim Society; Rabbi Julie Schonfeld of the Rabbinical Assembly, the international association of rabbis from Judaism’s Conservative movement; and the Rev. Leith Anderson, president of the National Association of Evangelicals.